Mercurial > repos > blastem
view nor.c @ 2069:8e51c0c3f2e3 segacd
Initial attempt at implementing the Sega CD graphics hardware
author | Michael Pavone <pavone@retrodev.com> |
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date | Sun, 30 Jan 2022 19:55:33 -0800 |
parents | 1f745318f10a |
children | d74d3998482c |
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#include "genesis.h" #include <stdlib.h> #include <string.h> #include "util.h" enum { NOR_NORMAL, NOR_PRODUCTID, NOR_BOOTBLOCK }; enum { NOR_CMD_IDLE, NOR_CMD_AA, NOR_CMD_55 }; //Technically this value shoudl be slightly different between NTSC and PAL //as it's defined as 200 micro-seconds, not in clock cycles #define NOR_WRITE_PAUSE 10690 void nor_flash_init(nor_state *state, uint8_t *buffer, uint32_t size, uint32_t page_size, uint16_t product_id, uint8_t bus_flags) { state->buffer = buffer; state->page_buffer = malloc(page_size); memset(state->page_buffer, 0xFF, page_size); state->size = size; state->page_size = page_size; state->product_id = product_id; state->last_write_cycle = 0xFFFFFFFF; state->mode = NOR_NORMAL; state->cmd_state = NOR_CMD_IDLE; state->alt_cmd = 0; state->bus_flags = bus_flags; state->cmd_address1 = 0x5555; state->cmd_address2 = 0x2AAA; } void nor_run(nor_state *state, m68k_context *m68k, uint32_t cycle) { if (state->last_write_cycle == 0xFFFFFFFF) { return; } if (cycle - state->last_write_cycle >= NOR_WRITE_PAUSE) { state->last_write_cycle = 0xFFFFFFFF; for (uint32_t i = 0; i < state->page_size; i++) { state->buffer[state->current_page + i] = state->page_buffer[i]; } memset(state->page_buffer, 0xFF, state->page_size); if (state->bus_flags == RAM_FLAG_BOTH) { //TODO: add base address of NOR device to start and end addresses m68k_invalidate_code_range(m68k, state->current_page, state->current_page + state->page_size); } } } uint8_t nor_flash_read_b(uint32_t address, void *vcontext) { m68k_context *m68k = vcontext; genesis_context *gen = m68k->system; nor_state *state = &gen->nor; if ( ((address & 1) && state->bus_flags == RAM_FLAG_EVEN) || (!(address & 1) && state->bus_flags == RAM_FLAG_ODD) ) { return 0xFF; } if (state->bus_flags != RAM_FLAG_BOTH) { address = address >> 1; } nor_run(state, m68k, m68k->current_cycle); switch (state->mode) { case NOR_NORMAL: if (state->bus_flags == RAM_FLAG_BOTH) { address ^= 1; } return state->buffer[address & (state->size-1)]; break; case NOR_PRODUCTID: switch (address & (state->size - 1)) { case 0: return state->product_id >> 8; case 1: return state->product_id; case 2: //TODO: Implement boot block protection return 0xFE; default: return 0xFE; } //HERE break; case NOR_BOOTBLOCK: break; } return 0xFF; } uint16_t nor_flash_read_w(uint32_t address, void *context) { uint16_t value = nor_flash_read_b(address, context) << 8; value |= nor_flash_read_b(address+1, context); return value; } void nor_write_byte(nor_state *state, uint32_t address, uint8_t value, uint32_t cycle) { switch(state->mode) { case NOR_NORMAL: if (state->last_write_cycle != 0xFFFFFFFF) { state->current_page = address & (state->size - 1) & ~(state->page_size - 1); } if (state->bus_flags == RAM_FLAG_BOTH) { address ^= 1; } state->page_buffer[address & (state->page_size - 1)] = value; break; case NOR_PRODUCTID: break; case NOR_BOOTBLOCK: //TODO: Implement boot block protection state->mode = NOR_NORMAL; break; } } void *nor_flash_write_b(uint32_t address, void *vcontext, uint8_t value) { m68k_context *m68k = vcontext; genesis_context *gen = m68k->system; nor_state *state = &gen->nor; if ( ((address & 1) && state->bus_flags == RAM_FLAG_EVEN) || (!(address & 1) && state->bus_flags == RAM_FLAG_ODD) ) { return vcontext; } if (state->bus_flags != RAM_FLAG_BOTH) { address = address >> 1; } nor_run(state, m68k, m68k->current_cycle); switch (state->cmd_state) { case NOR_CMD_IDLE: if (value == 0xAA && (address & (state->size - 1)) == state->cmd_address1) { state->cmd_state = NOR_CMD_AA; } else { nor_write_byte(state, address, value, m68k->current_cycle); state->cmd_state = NOR_CMD_IDLE; } break; case NOR_CMD_AA: if (value == 0x55 && (address & (state->size - 1)) == state->cmd_address2) { state->cmd_state = NOR_CMD_55; } else { nor_write_byte(state, state->cmd_address1, 0xAA, m68k->current_cycle); nor_write_byte(state, address, value, m68k->current_cycle); state->cmd_state = NOR_CMD_IDLE; } break; case NOR_CMD_55: if ((address & (state->size - 1)) == state->cmd_address1) { if (state->alt_cmd) { switch(value) { case 0x10: puts("UNIMPLEMENTED: NOR flash erase"); break; case 0x20: puts("UNIMPLEMENTED: NOR flash disable protection"); break; case 0x40: state->mode = NOR_BOOTBLOCK; break; case 0x60: state->mode = NOR_PRODUCTID; break; } } else { switch(value) { case 0x80: state->alt_cmd = 1; break; case 0x90: state->mode = NOR_PRODUCTID; break; case 0xA0: puts("UNIMPLEMENTED: NOR flash enable protection"); break; case 0xF0: state->mode = NOR_NORMAL; break; default: printf("Unrecognized unshifted NOR flash command %X\n", value); } } } else { nor_write_byte(state, state->cmd_address1, 0xAA, m68k->current_cycle); nor_write_byte(state, state->cmd_address2, 0x55, m68k->current_cycle); nor_write_byte(state, address, value, m68k->current_cycle); } state->cmd_state = NOR_CMD_IDLE; break; } return vcontext; } void *nor_flash_write_w(uint32_t address, void *vcontext, uint16_t value) { nor_flash_write_b(address, vcontext, value >> 8); return nor_flash_write_b(address + 1, vcontext, value); }